The clay-fields of the valley of the Po produced the brickwork of Cremona, Pavia, Crema, Chiaravalle, and Vercelli.

To their quarries of _mandorlato_ the Veronese builders owed the peach-bloom colours of their columned aisles.

Carrara provided the Pisans with mellow marble for their Baptistery and Cathedral; Monte Ferrato supplied Pistoja and Prato with green serpentine; while the _pietra serena_ of the Apennines added austerity to the interior of Florentine buildings.

Again, in other instances, we detect the influence of commerce or of conquest.

The intercourse of Venice with Alexandria determined the unique architecture of S.Mark's.